Sulfonyl nitrene

Sulfonyl nitrenes react with benzene to produce appreciable yields of aromatic substitution products. The nitrene thermally generated in benzene from 229 gives a monosubstitution product. When the reaction is carried out in mesitylene as a solvent, the two sulfonylnitrenes react with mesitylene to afford 230 (equation 140)135. 

Insertion (see 12-12). Nitrenes, especially acyl nitrenes and sulfonyl nitrenes, can insert into C—H and certain other bonds, for example. 

V. ADDITION OF SULFONYL CARBENES AND SULFONYL NITRENES A. Sulfonyl Carbenes... 

Treatment of sulfonylamide tetrabutylanmionium salts RS02NH Bu4N+ in benzene with Xep2 gives the corresponding At-sulfonylazepines (68) via a proposed sulfonyl nitrene intermediate." ... 

For monographs, sec Scriven Azides and Nitrenes-, Academic Press New York, 1984 Lwowski Nitrenes. Wiley New York. 1970. For reviews, see Scriven React. Interned. (Plenum) 1962,2, 1-54 Lwowski React. Interned. (Wiley) 1985, 3. 305-332.1981, 2, 315-334. 1978, 1. 197-227, Angew. Chem. Ini. Ed. Engl. 1967, 6. 897-906 [Angew. Chem. 79. 922-931) Abramovitch, in McManus. Ref. 1. pp. 127-192 Hiinig Helv. Chim. Acta 1971, 54, 1721-1747 Belloli J. Chem. Educ. 1971, 48, 422-426 Kuznetsov Ioffe Russ. Chem. Rev. 1989, 58, 732-746 (N- and O-nitrenes) Mcth-Cohn Acc. Chem. Res. 1987,20,18-27 (oxycarbonylnitrenes) Abramovitch Sutherland Fortsch. Chem. Forsch. 1970, 16. 1-33 (sulfonyl nitrenes) Ioffe Kuznetsov Russ. Chem. Rev. 1972, 41, 131-146 (N-nitrenes). 

Relative reactivity studies with primary, secondary, and tertiary C-H bonds have revealed the following order of selectivity phenylnitrene > carbethoxynitrene > sulfonyl-nitrene > car bene.88 ... 

Acyl nitrenes are highly reactive but unfortunately their precursors, acyl azides, are chemically reactive, e.g. they acylate amino groups. While sulfonyl- and alkoxycarbonyl azides are somewhat less reactive than acyla-zides, and the nitrenes derived from them are highly reactive (Lwowski, 1970 and for sulfonyl nitrenes see Abramovitch et al., 1981 and references therein), the azides must be irradiated in the UV, below 300 nm. Phos-phorylnitrenes are the most reactive nitrenes known and will insert into CH bonds in the presence of hydroxyl groups (Breslow et al., 1974). Again, photolysis occurs at ultraviolet wavelengths. 

D. S. Brcslow, Sulfonyl Nitrenes in Nitrenes (ed. W. Lwowski), John Wiley and Sons, New York, 1970, pp. 245-303. 

However, when sulfonyl azides (84) are heated (120-150°C), they decompose with loss of nitrogen and the transient formation of the sulfonyl nitrene (88) (Scheme 58), which is the basis of many of their reactions. 

The electron-deficient sulfonyl nitrene (88) can insert into electron-rich carbon-hydrogen bonds, abstract hydrogen atoms, and add to double bonds and aromatic rings. These reactions may be initiated by acids, heat, light and transition metals. The reactions are illustrated by heating methanesulfonyl azide (89) with bezene (23) (Scheme 59). Here, the electrophilic sulfonyl nitrene (90) adds to the electron-rich aromatic double bond, but the kinetically favoured azepine(91) rearranges to give the thermodynamically favoured N-phenyl sulfonamide (92) (Scheme 59). 

Sultams may also be obtained by flash vacuum pyrolysis (FVP) of sulfonyl azides the reaction occurs via the sulfonyl nitrene (182) which contains an electron-deficient nitrogen atom and consequently rearranges by proton transfer to give the sultam (183) (Scheme 76). 

Similar to singlet carbenes, singlet nitrenes (R-N ), the nitrogen analog of carbenes, are also known to insert into C-H bonds." Acyl nitrenes and sulfonyl nitrenes insert rather readily in C-H bonds [Eq. (6.133)] ... 

Nitrenes undergo addition reactions to neutral nucleophiles.60 51 Accordingly, they add to the nitrogen atom of pyridines, forming iV-imines. This method of preparation was described first by Curtius et a/.62-66 They heated aromatic sulfonyl azides in pyridine and obtained various A-sul-fonylimines [Eq. (5) ] the structures of which were not at that time recognized. They formulated sulfonyl nitrenes as intermediates in this reaction. 

Recently, Porter and Waisbrot demonstrated that azidoformyl compounds containing a hindered phenolic antioxidant moiety decomposed thermally to form carbalkoxynitrene intermediates that insert into a natural rubber matrix (9). This chapter describes the preparation and use of antioxidants containing the sulfonyl azide group, that decomposes to liberate nitrogen and the sulfonyl nitrene species when heated either in a vulcanization process or in an extruder. 

Both alkane and arene sulfonyl nitrenes insert into the carbon-hydrogen bonds of saturated hydrocarbons although not as efficiently as carbenes (10). 

To prepare several sulfonyl azides containing the required antioxidant moiety, an intermediate was chosen that would react readily with known hindered phenols and that would still possess the requisite precursor for sulfonyl nitrene insertion. Therefore, 4-isocyanatobenzenesul-fonyl azide was prepared following the procedure described by Dan-haeuser and Pelz (16). 

Nitrenes are also highly reactive species. Much less is known about their structure and reactivity compared with that of carbenes. Besides C-nitrenes, N-, 0-, and sulfonyl nitrenes are also known (reviews N- and O-nitrenes Kuznetsov and Ioffe, 1989 sulfonyl nitrenes Abramovitch and Sutherland, 1970). 

Benzo derivative (46) was formed in 7% yield through intramolecular Friedel-Crafts acylation of an acyclic sulfamoyl chloride (Equation (15)) <920PP463>, while the benzo-2,1-thiazocine derivative (48) was formed in 30% yield through the intermecliacy of the sulfonyl nitrene, generated thermally from the corresponding sulfonyl azide, which underwent intramolecular insertion into an aromatic C—H bond (Equation (16)) <81CC1087>. 

Scheme 6.33 Insertion of sulfonyl nitrene into an aromatic ring.

A few cases of the use of nitrene chemistry to form SCNPs have been reported in the literature. In one example, Pu and coworkers took advantage of the sulfonyl azide moiety, which is capable of releasing nitrogen at high temperature to form sulfonyl nitrenes. Due to the highly reactive nature of the resultant nitrene, the cross-links that are formed are not well-defined. In a... 

Suberic acid, 506 Substrate analogs, 8, 9 Subtilisin, 22, 27, 75, 206, 207 Subtilisin BPN, 215 Succinimide esters, 96 Sucrase-isomaltase complex, 377,379 Suicide reagents, 9, 10 Sulfonyl azides, 78 a-Sulfonyl nitrenes, 78 Sulfoxides, 135... 

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